Gabapentin is a generic term used to identify the chemical compound (1-aminomethyl)-1-cyclohexaneacetic acid ##STR1## It is useful in therapy of certain cerebral disorders such as certain forms of epilepsy, faintness attacks, hypokinesia, and cranial traumas. U.S. Pat. Nos. 4,024,175 and 4,087,544 cover the compound and its uses. They also disclose an acid salt, i.e., gabapentin hydrochloride hydrate in a ratio of 4:4:1 and a sodium salt of gabapentin hydrate in a ratio of 2:1. U.S. Pat. No. 4,894,476 describes gabapentin monohydrate and a process for producing it. These patents are incorporated by reference.
The patents describe various processes for the preparation of this and similar compounds of general formula ##STR2## wherein R.sub.1 is a hydrogen atom or a lower alkyl radical and n is 4, 5, or 6 and the pharmaceutically acceptable salts thereof, which depend upon known methods used for the preparation of primary amines or amino acids.
Examples of the syntheses end in an isocyanate or urethane that can be converted into the desired (1-aminomethyl)-1-cyclohexaneacetic acid by acidic hydrolysis to give an acid or basic hydrolysis to give a basic salt or followed by acidification to give an acid salt.